I will almost surely vote for a third party candidate, for a couple of reasons.
First, as a policy based traditional conservative neither the Democrats nor the Republicans represent what I believe. The Republicans used to be pretty close, but this new evolution of the GOP is no longer conservative in the good sense. So, I'm considering finding a candidate who more closely aligns with conservative views.
Second, given I am dissatisfied with what the two parties are providing us, it makes sense to do anything, however small, to help break the duopoly those parties have on the election marketing process. The biggest thing among those is the debates, which have a 15% polling requirement that guarantees third parties can't qualify, and by not letting them qualify it keeps people from hearing their ideas on the biggest stage which might help them grow support. So anything that would apply pressure to changing that, such as a unexpectedly high percent from a candidate, is a good thing.
In all honesty, my vote for President is meaningless if I look at it from helping determine who wins the electoral college votes from my state. I live in a deep red state which will vote for the Republican candidate no matter what. My biggest opportunity to actually influence is in the Republican primaries where I support candidate who have conservative policy ideas that are focused on improving the opportunity to succeed for everyone. Those are hard to find right now, but particularly at the state level we still have some. If I lived in a purple state, I would seriously consider voting for Harris because I would really like for the MAGA/traditional Republican internal conflict to be won by the traditionals - and Trump losing would potentially help in that regards.